Polymeric Composition for Cement Based Substructures

ABSTRACT

The present invention is directed to a composition capable of inhibiting moisture vapor emission from concrete structures and enhancing adhesion of a finish material to the concrete structure comprising an aqueous mixture of a first copolymer of mer units formed from vinylidene halide and a C1-C2 alkyl acrylate with a second copolymer of mer units formed from vinylidene halide and a C4-CS alkyl acrylate and to the method of forming a moisture barrier/adhesion promoter coating on concrete comprising applying from 2.8 to 5.6 liters (0.75 to 1.5 gallons) of an aqueous carrier having from 10 to 50 weight percent of the mixture of copolymers stated above per 14 m2 (150 square feet) of the free surface of a concrete structure.

BACKGROUND OF THE INVENTION

The present invention relates to polymeric compositions formed from amixture of prescribed copolymers in certain defined ratios and the useof said composition to provide enhanced cement based buildingstructures. The subject composition provides a water vapor barriercoating for cement based structures and an enhanced adhesion agent formaterials applied thereto. Further, the composition, when applied togreen (uncured) cement based structures, causes resultant curedstructures to have enhanced strength and integrity.

Cement compositions and materials, such as concrete, cement block andthe like, are common materials used in the construction industry. Theterm “concrete” and “cement” are each used herein and in the appendedclaims to refer to materials and structures formed of cement basedcompositions. The present invention is described by use of concretebuilding structures, such as slabs and the like, used as buildingflooring and wall structures although it is intended that other forms ofcement based compositions be included in the present invention.

When concrete is poured, there is a period of time required to attaininitial solidification of the concrete mixture. After initial setting,the concrete cures over an extended period of time during whichhydration of the silicate and aluminate components develop and theexcess water of the initial mix is lost. It is only after this extendedperiod that the concrete has developed its full strength. In order forthe concrete to properly cure and achieve its designed strength, therate of water loss must be kept low. Such concrete is termed “green”structures while they are in their initial formation and in thepartially cured state. Thus, it is well known that concrete structurescontain and expel water for extended periods of time after initialformation.

When a concrete structure is formed directly adjacent to the ground orwhen grading of the surrounding terrain is complete, the structure incontact with ground material is continuously feed water from the groundby hydrostatic pressure. This is especially true when the concrete formsa grade-level or below grade-level flooring of a building or a belowgrade-level wall. In the case of a wall structure, the outside of thewall that is adjacent to the terrain is normally coated with acomposition or structural forming membrane which inhibits thepenetration of water into the wall material. Similarly, flooring slabsare normally poured over a bed of gravel and a plastic membrane toinhibit penetration of water into the slab formation. In both instances,the membranes are known to be less than completely effective due, inpart, to imperfections in the membrane, imperfections generated duringformation and pouring of the concrete, during backfill of the terrainagainst the wall structure, and from deterioration of the membrane overtime. Thus, concrete structures have a tendency to take up water andexpel the water through its free surface over extended periods of time.

When the concrete structure remains as formed and has an uncovered freesurface, the water that escapes from the structure may be of asufficiently small rate and in a form (e.g. water vapor) to beunnoticeable and inconsequential. However, when the concrete structureis intended to act as a substructure to be covered by additionalmaterial to form a finished structure, the additional material tends totrap the moisture. It has been previously suggested to coat concretesurfaces with various paints, including those based on an acrylatepolymer in attempts to form water barrier coating. Such coatingsgenerally exhibit poor adhesion and tend to spall from the concretestructure. These adverse effects cause deterioration of the appliedfinishing material as well as the bonding agent used to adhere finishingmaterials to the concrete substructure. Further, the trapped moisturemay cause mold and other undesired formations to occur.

It is highly desired to be able to apply a sealer/coating compositioncapable of inhibiting moisture vapor emission from concrete structures,to have high adhesion to concrete structures and to enhance the adhesionof a concrete substructure to finishing materials commonly used inbuilding industry. It is also highly desired to have a compositionhaving the above properties that can be applied to green concretesubstructures as well as fully cured concrete substructures to, thereby,enhance job scheduling and completion. It is further desirable toinhibit evaporation of water during initial curing of freshly formedconcrete structures to allow hydration to occur slowly during curing andthereby produce a resultant structure having high strength andintegrity.

SUMMARY OF THE INVENTION

The present invention is directed to a composition capable of inhibitingmoisture vapor emission from concrete structures and enhancing adhesionof a finish material to the concrete structure comprising an aqueousmixture of a first copolymer of vinylidene halide and a C₁-C₂ alkylacrylate with a second copolymer of vinylidene halide and a C₄-C₅ alkylacrylate and to the method of forming a moisture barrier/adhesionpromoter coating on concrete comprising applying from 2.8 to 5.6 liters(0.75 to 1.5 gallons) of an aqueous carrier having from 10 to 50 weightpercent of the mixture of copolymers stated above per 14 m² (150 squarefeet) of the free surface of a concrete structure. The concretestructure unexpectedly exhibits enhanced low water vapor emission,enhanced adhesion of finished material applied thereto and inhibitspalling of the applied coating composition from the concrete surface.Further, it has been unexpectedly found that the composition of thepresent invention can be applied to surfaces of uncured or partiallycured concrete structures to cause reduced evaporation of the waterthere from and, thus, results in formation of a structure of superiorstructural strength and integrity.

DETAILED DESCRIPTION OF THE INVENTION

It has been unexpectedly found that a mixture of two distinctcopolymers, when combined together and applied to concrete formations inprescribed amounts, forms a coating capable of adhering to the concreteformation surface, providing a moisture vapor emission barrier andacting as an interfacial adhesion enhancer between the concrete surfaceand adhesive bonding agents of finish coverings.

It has also been unexpectedly found that the mixture of copolymers, whenapplied as an aqueous composition to the surface of uncured or partiallycured concrete structures, provides a means of causing the resultantcured structure to have enhanced strength and integrity. To reduce waterevaporation during the curing process, one conventionally appliesblankets and/or repeated application of water to the surface of thestructure while curing. Besides such applications being labor intensiveand costly, the application of blankets to uncured surfaces may mar theformed structural surface and repeated application of water may reducethe strength of the resultant structure at and adjacent to its surface.These undesired properties are thus eliminated by a single applicationof an aqueous dispersion of the present mixture of first and secondcopolymers described herein below.

It has also been unexpectedly found that the present mixture provides acoating that exhibits high adhesion as well as wear and abrasionstrength (tested under ASTM D4060-10) to concrete surfaces, even thosethat have been steel troweled to provide an ultra-smooth surface. Thisphenomenon is may be due to the ability of the mixture to becomeincorporated into portion of the concrete adjacent to the treatedsurface. Aqueous dispersions of prior art polymers, when applied toconcrete surfaces, cause the surface layer of the structure to havereduced strength and adhesion properties and, therefore, it isprescribed that such surface layer be mechanically removed beforeconventional application of a finish floor covering. Finally, it hasbeen found that the present mixture causes the surface of the concretestructure to have a substantially neutral pH of lower than about 8. Thisprovides a surface that is substantially inert to finishing materialsapplied thereto.

The mixture is formed of a first copolymer formed from vinylidene halideand a C₁-C₂ alkyl acrylate, preferably from vinylidene chloride andmethyl acrylate monomers. The formed copolymer has resultant C₁-C₂ alkylacrylate mer units in from 5 to 40, preferably from 5 to 20 and mostpreferably from 5 to 15 percent by weight of the copolymer. Theremainder of the first copolymer is composed of vinylidene halide merunits. The copolymer may also contain minor amounts (less than or equalto the weight percentage of the acrylate mer units) of mer units derivedfrom other ethylenically unsaturated monomers capable of copolymerizingwith the required monomers taught above such as, for example, olefins asethylene, propylene and the like; acrylonitrile and the like. The firstcopolymer is conventionally formed by free radical polymerization and iscommercially available.

The mixture must further have a second copolymer which is formed from avinylidene halide and a C₄-C₅ alkyl acrylate, preferably from vinylidenechloride and butyl acrylate, monomers. The formed copolymer hasresultant C₄-C₅ alkyl acrylate mer units in from 3 to 40, preferablyfrom 3 to 15, and most preferably from 3 to 10 percent by weight of thecopolymer. The remainder of the second copolymer is composed ofvinylidene halide mer units. The copolymer may also contain minoramounts (less than or equal to the weight percentage of the acrylate merunits) of mer units derived from other ethylenically unsaturatedmonomers capable of copolymerizing with the required monomers taughtabove such as, for example, olefins as ethylene, propylene and the like;acrylonitrile and the like. The polymer is conventionally formed by freeradical polymerization and is commercially available.

The first and second copolymers forming the desired mixture should bepresent in a weight ratio of from 90:10 to 10:90, preferably from about80:20 to 10:90 and more preferably from 75:25 to 20:80. In allinstances, both the first and second copolymers described above must bepresent to provide the enhanced properties which are the achieved goalsof the present invention. When the mixture is formed of first and secondcopolymer in weight ratios of from 90:10 to 60:40(with from 80:20 to70:30 being preferred and about 75:25 forming the most preferred mixturewithin this range), i.e. having high content of C₁-C₂ alkylacrylate/vinylidene halide copolymer, the mixture is preferably appliedas a dispersion having low concentration of from about 10 to 30 weightpercent of the mixture of copolymers. It is preferable to have suchdispersions applied as low dosage, multiple applications separated bydrying periods of from 0.5 to 1.5 hours between applications. When themixture is formed of first and second copolymer in weight ratios havinglower concentration of C₁-C₂ alkyl acrylate/vinylidene halide copolymer,i.e. 50:50 to 10:90 (preferably from 40:60 to 25:75 and most preferablyfrom 30:70 to 35:65), it is preferable to apply the subject mixture as ahigh solid concentration dispersion having from 25 to 50 weight percentof the mixture of copolymers. In this embodiment, a single, high dosageapplication of the dispersion is normally sufficient, although multipleapplications may be used. The ability to be applied in a singleapplication is highly desired as the labor and the time for application,taking account of the interim drying times when multiple applicationsare used, are minimized. The high concentration dispersion can beapplied as a relatively thick coating and provides, when dried, apliable, abrasion resistant coating exhibiting extremely high adhesionand moisture barrier properties with respect to the concrete substrate.

The mixture of the first and second copolymers within the above ratiorange have been unexpectedly found to achieve the desired combination ofproperties of providing high reduction in moisture vapor emission fromthe free (treated) surface of the concrete formation, that is, theexposed surface, forming a layer of concrete structure adjacent to theexposed surface which is impregnated with the polymer mixture, forming afilm on the free surface of the concrete structure which has a high bondstrength with the concrete surface, does not exhibit deterioration inthe form of cracking and the like so that it maintains its moisturebarrier properties over time; and at the same time provides goodinterfacial bonding properties between the concrete surface and theadhesive coat used for bonding conventional surface finish materialthereto. The subject composition is capable of readily forming amoisture barrier coating on concrete surfaces which provide a means ofenhancing the use life of finished materials applied thereto, includingthose that are applied by adhesives (e.g. thin set cement,polyurethanes, epoxy systems and the like), or directly thereon (e.g.floating floor coatings and the like).

The two copolymers, either separately or as a prior combined mixture,are mixed with water to provide an aqueous dispersion having from 10 to50 weight percent of the combined copolymer. As stated above, thedispersion has preferably from 10 to 30, with from 15 to 30 and from 20to 30 weight percent of the combined copolymer when the mixture iscomposed of a high content of the C₁-C₂ alkyl acrylate/vinylidene halidecopolymer while the applied dispersion preferably has a high solidcontent of from 25 to 50, preferably from 30 to 40 weight percent solidsof mixtures having lower content of the C₁-C₂ alkyl acrylate/vinylidenehalide copolymer.

Normally, the resultant dispersion of the polymers in water is achievedby high shear mixing with the resultant mixture consisting of smallparticles of the copolymers in particle size of from about 50 to about250 nm. Conventional emulsifiers and dispersants may be used to aid informing a uniform composition. The resultant dispersions should beacidic with a pH of from about 1.5 to 3.5, preferably a pH of from about2 to 3 with from 2.2 to 2.7 being most preferred. The pH can be adjustedto the desired range by additions of small amounts of mineral acid, asneeded. The aqueous dispersion may contain small amounts (normally lessthan about 5 weight percent) of UV stabilizers, dispersants,emulsifiers, stabilizers and/or colorants (optionally added to aid inassuring complete application coverage).

Aqueous dispersions of each of the first and of the second copolymer maybe shipped in concentrated form, mixed together, and further dilutedwith water at blending facilities using conventional mixers, such ashigh shear mixers. Further, aqueous dispersions of the mixture of firstand second copolymer may be shipped in concentrated form to the job siteand mixed with fresh water to reduce the concentration to theappropriate range for the mode of application and the resultant coatingdescribed herein above. The dispersion, applied as a single or asmultiple coats, should be sufficient to form a moisture barrier/adhesionpromoter coating on the targeted concrete substructure.

The aqueous dispersion having the subject copolymer mixture can bereadily applied to the concrete surface by spray, brush, high nap paintroller, with the aid of a squeegee or the like to provide a thin,substantially uniform coating of the dispersion onto the concretesurface. The dispersion, as solids, should be applied to provide fromabout 0.9 to 9 pounds (0.4 to 4 kg) of the solids of the mixture ofcopolymers per 14 m² (150 square feet) to the free surface of a concretestructure upon evaporation of the water media. When the copolymermixture has a high content of C₁-C₂ alkyl acrylate/vinylidene halidecopolymer, the mixture is preferably applied as a low concentrationdispersions having from about 10 to 30 weight percent of the mixture ofcopolymers. The dispersion should preferably be applied in multiplecoats to result in a coating having from 1.9 to about 5 pounds (0.8 to2.3 kg), preferably from 2.5 to 3 pounds (1.1 to 1.4 kg) of solidmixture per 14 m² (150 ft²) of free surface of the concrete structure.In such applications it is preferred to apply the mixed copolymerdispersion in at least two applications when over 2 pounds (0.9 kg) ofsolids are applied to form the coating, with a 0.5 to 1.5 hour dryingtime between coats. The coats are best applied by a first coatapplication in one direction with a second coat application in adirection that is transverse to the first coat application direction.When the copolymer mixture has a low content of C₁-C₂ alkylacrylate/vinylidene halide copolymer, the mixture is preferably appliedas a high concentration dispersions having from about 25 to 50 weightpercent of the mixture of copolymers. Such dispersions may preferably beapplied in a single application to result in a coating having from 4 toabout 9 pounds (1.8 to 4 kg), preferably from 5.5 to 9 pounds (2.5 to 4kg) of solid mixture per 14 m² (150 ft²) of free surface of the concretestructure. The resultant coating is thus applied in one applicationwhich is both time and labor saving yet provides a tough, flexiblefinished coating.

Dispersions of the copolymer mixture can be applied to green as well assubstantially fully cured concrete formations to achieve the desiredproperties. Usually the dispersion can be applied at any time after 12hours (and as short a time as 3 hours) from the formation of thestructure. Further, the dispersion, even when used with low amounts ofsolid content, dries within six, most times within four, hours ofapplication. The drying time for the applied dispersion has been foundnot to be dependent on the ambient conditions of the environment of theslab being treated. The dispersion has been found to dry to the desiredbarrier coating and barrier concrete surface layer independent of thedegree of cure of the concrete substrate to which it is applied. Thus,this allows for installation of finish material within short periods anddoes not hinder the progress of building schedules. The formula has beenapplied to green concrete with an epoxy applied four hours later. It hasbeen unexpectedly found to completely eliminate out gassing that almostalways is known to cause blistering and pin holing of epoxy when used onnew concrete.

The application of the present mixture to uncured or partially curedconcrete structures provides a means for allowing the concrete to curein a desired slow manner to produce a structure of enhanced strength andintegrity without the use of application of a covering, such as a tarp,or repeat water spray applications to the structure which are theconventional, though labor intensive, manners used to reduce waterevaporation. The single application of aqueous dispersions of the abovedescribed mixtures of copolymers, especially those formed with first andsecond copolymers in weight ratios of 50:50 to 10:90, and morepreferably from 35:65 to 10:90, as a means of inhibiting waterevaporation during the initial curing of green concrete structures,achieves the desired results without the undesired laborious applicationof tarps or water to the structure's free surface. Further, applicationof the present mixture of copolymers substantially eliminates anypotential of marring the surface by covering it with tarps and the likeor by reducing the strength of the surface layer of the concrete bywater spray application. Instead, it has been found that the mixtures ofcopolymers described herein becomes adsorbed (or absorbed) in andbecomes an integral part of the layer of the green concrete structureadjacent to the treated surface. It has been found by observation andmicroscopic examination that the application of the above describedmixture of copolymers does not remain on the surface but, instead,readily penetrates (For normal application, the mixture penetrates todepths ranging from about 15 to 25 mils, such as an average of about 18mils, below the surface) into the structure adjacent to the treatedsurface causing the resultant structure to achieve a structure free ofblemishes and having enhanced integrity and strength.

It has been found that when the presently prescribed mixtures ofcopolymers are applied as substantially uniform coating to concretesurfaces in the amounts stated above, one attains a film which inhibitswater vapor emission (MVER) or Moisture Vapor Emission Rate according toASTM 1869 to less than 3 pounds and most often to less than 2.5 poundsper 1000 ft² per 24 hours (Generally referred to in pounds). ASTM F710specifically notes that concrete is suitably dry when the moisture vaporemission rate does not exceed three (3) lbs. of water per 1000 squarefeet per 24 hours when tested in accordance with the test method of ASTMF1869. The three pound point is used as a recognized benchmark bymanufacturers of floor covering, adhesive and resinous coating productsas it is known not to cause adverse effects due to moisture. At the sametime, the formed coating of the present invention exhibits high adhesionto the concrete surface, can be readily applied to green as well asfully cured concrete structures and provides good compatibility andadhesion with a wide range of adhesives used in the industry whenapplying finished surfaces.

The materials that are desirable to act as finishing coverings includeflooring products, such as, for example, solid wood planking, woodlaminates, polymeric laminates (linoleum and the like products),vinyl/VCT, rubber, epoxy flooring systems, various tile flooring,carpeting and self-leveling cement underlayment and wear surfaces. Thesematerials are conventionally applied to a concrete slab by applying anadhesive composition suitable for the particular flooring product.Applications are conventionally done with notched trowel to apply aprescribed and even amount of adhesive for the adhesion of the finishcovering. The present mixture has been unexpectedly found to becompatible and have high adhesion properties with respect to a widevariety of adhesives, such as acrylic latex, transitional pressuresensitive adhesives, polyurethanes and the like conventionally used forbonding the finished covering material to the concrete sub-floorstructure.

The following examples are given for illustrative purposes only and arenot meant to be a limitation on the invention described herein or on theclaims appended hereto. All parts and percentages given in thedescription, examples and appended claims are by weight unless otherwisestipulated. Further all ranges or numbers provided herein shall bedeemed to specifically disclose all subset ranges within each givenrange.

Example I

A series of 12″ round concrete slabs were cast using commerciallyobtained bags of dry concrete mix (Ready-Mix) which were mixed withclean water using instructions applicable to the 4,000 psi bag mixture.The uniform concrete mixture was then poured into molds formed of 3.5″high steel frame over a rubber base. This was performed by applyingthree lifts, each being vibrated and compacted then smooth trowelfinished. Within 48 hours, the frame was removed and sample slab curedfor 28 days. A 100% solids epoxy (3 coats) was then applied to the 3.5″side and 2″ perimeter of the top and bottom leaving a 9.75″ diameterexposed concrete area on the center of the top and bottom of the sampleslab. This was allowed to cure for 7 days. The samples were then coatedwith a sufficient amount of an aqueous mixture having 22 wt. percentsolids of a mixture of first copolymer having 10 wt. % methyl acrylateand 90 wt. % vinylidene chloride and a second copolymer having 5 wt %butyl acrylate, 5 wt % acrylonitrile and 90 wt. % vinylidene chloride toprovide a solid coating at the rate of 2.8 pounds per 14 m² per coatwith two coats 1 hour apart. The aqueous composition had a pH of 2.After 4 hours, the samples were placed into the test apparatus to startwater vapor increase to desired amounts.

Aqueous dispersions having 22 wt. % solids of a 90:10 mixture ofvinylidene chloride/methyl acrylate copolymer with vinylidenechloride/butyl acrylate copolymer was applied over the surface of threeslab samples 12 hours after initial casting to represent applicationover “green” concrete slab. An additional three slabs were coated 30days after casting to represent fully cured concrete. The dispersioneasily spread using a one-quarter inch nap paint roller with two coatsapplied at the rate of 14 m² per gallon total for the two coats. In allcases the coatings were found to be dry to the touch in less than 0.5hours after application.

The moisture blocking ability (of the subject mixed copolymer coatingwas determined by measuring the moisture vapor emission rate (MVER) foreach sample according to the procedures of ASTM F 1869 beforeapplication of the coating and 28 days after application of the coating.The results given in Table 1 are the average for each set of threesamples. The apparatus used provided simulation of high moisture vaporpressure on the samples. The treated samples showed high barrier abilityand good retained adhesion between concrete and barrier coating.

In addition, a 50 mm diameter dolly had epoxy applied and was placed onthe copolymer coated concrete samples. Adhesion pull test were conductedaccording to ASTM D7234. The results are given in Table 1 herein below.

The above test procedure was repeated using coatings formed fromdispersions of varying ratios of the two copolymers. The coatings formedwith mixtures containing both copolymers preformed well for both MVERand adhesion. The coatings applied easily and yielded a surface showingno deterioration over time. The results are given in Table 1 below.

Example II

For comparative purposes, the tests described in Example I above, wereconducted using each of the copolymers separately. The results of thesetests are reported in Table II below. The results show that neithercopolymer, when used alone, formed a coating having the desiredproperties achieved with the present described mixture of copolymers.Coatings of VC/methyl acrylate exhibited substantially no adhesiveproperties with respect to the concrete to which it was applied.Further, the resultant VC/methyl acrylate coatings were brittle andshattered under light impact forces. Thus, coatings of VC/methylacrylate would not produce a suitable coating to impart moistureblocking and adhesion properties presently achieved by the presentinvention. Further, the results show that VC/butyl acrylate copolymer,when used alone, formed a coating having poor moisture blockingproperties (test values above 3.0 are unacceptable); the cured coatingexhibited micro-cracks throughout and the coating permeated less than 4mils into the cement substructure surface.

TABLE 1 VC/Methyl 90 85 80 75 70 60 30 Acrylate VC/Butyl 10 15 20 25 3040 70 Acrylate (wt. %) Moisture 30.02 24.25 16.49 20.74 19.73 19.9 19.7Blocking to to to to to to to (lbs) 2.51 2.92 1.67 2.00 1.84 2.53 2.15Adhesion 32.75 106.3 317.5 387.6 192.7 84.3 324 Pull Test (lbs) Dry Timeto 0.1 3.4 5.3 9.2 2.5 14.0 Touch (hr) (at 70° F. RH at 50%)Observations Spread Spread Spread Spread Spread Spread and Spreads andand cover and cover and and cover and cover cover evenly covers evenlyevenly evenly cover evenly evenly and easily; and easily; and and evenlyand and no adsorbs into easily; no easily; no and easily; no easily; nodeterioration slab; produces deterio- deterio- easily; deterio- deterio-of covering flexible ration of ration of no ration of ration of overtime coating after covering covering deterio- covering covering cure; noover time over time ration of over time over time deterioration coveringover time over time

TABLE II VC/Methyl 100  0 Acrylate VC/Butyl  0 100 Acrylate (wt. %)Moisture 20.25 18.22 Blocking to to (lbs) 2.65 3.25 failed Adhesion  0  300.5 Pull Test failed (lbs) Observations Formed brittle coating;Formed coating having micro- shattered under low cracks throughout;weight impact high PERMS

Example III

An aqueous dispersion having 40 wt. % solids of a 30:70 mixture ofvinylidene chloride/methyl acrylate copolymer with vinylidenechloride/butyl acrylate copolymer was tested for abrasion resistanceaccording to the test method defined under ASTM D4060-10 (“Standard TestMethod for Abrasion Resistance of Organic Coating by Taber Abraser”) andfor acid/alkali resistance according to the test method of ASTMC1315-11. Four test panels of 13×9×0.5 inch (330×229×13 mm) formed ofwhite cement mortar were fabricated in accordance with ASTM D1734-07entitled “Standard Practice for Making Cementitious Panels for TestingCoatings”. The panels were steel trowel finished and two of the panelswere coated by spraying the aqueous dispersion of 30:70 mixture thereonto give a 12.7 ml coating per 0.85 ft² 0.26 m². The coatings wereapplied to the panels under moist conditions approximately three hoursafter placing the fresh mortar. All four panels were left to cure at73+/−2° F. (23+/−3° C.) and RH of 50+/−2%. After two days of curing, 4×4inch (17×17 mm) coupons were cut from the panels for Taber andacid/alkali tests.

The results of triplicate samples are given in Tables III and IV below.

TABLE III Taber Abrasion Test Coated Samples Wear Wear Wear Wear Wt. Wt.Wt. Wt. Wt. index index index index Initial 25 50 75 100 25 50 75 100sample g. cycle cycle cycle cycle cycle cycle cycle cycle 1 326.8 325.3323.2 321.5 320.2 60.0 72.0 70.7 66.0 2 325.2 323.9 322.2 320.2 319.252.0 60.0 62.7 60.0 3 327.7 326.7 325.5 324.3 323.2 40.0 44.0 45.3 45.0Avg. 50.67 58.67 59.56 57.00

Taber Abrasion Test Uncoated Control Samples Wear Wear Wear Wear Wt. Wt.Wt. Wt. Wt. index index index index Initial 25 50 75 100 25 50 75 100sample g. cycle cycle cycle cycle Cycle cycle cycle cycle 1 315.8 312.8310.6 309.9 307.6 120.0 104.0 78.07 82.0 2 313.8 310.7 308.9 307.7 306.7124.0 98.0 81.3 71.0 3 320.1 317.0 314.8 313.1 311.8 124.0 106.0 93.383.0 Avg. 122.67 102.67 84.22 78.67

TABLE IV Alkali/Acid Test Control Test (Uncoated) Coated Acid Nodiscoloration No blistering, no pinholes No discoloration Alkali Nodiscoloration No blistering, no pinholes No discoloration

1. A composition composed of an aqueous mixture of at least one firstcopolymer comprising mer units derived from vinylidene halide and merunits derived from C₁-C₂ alkyl acrylate, said mer units derived fromC₁-C₂ alkyl acrylate being present in from 5 to 40 weight percent of thefirst copolymer; and at least one second copolymer comprising mer unitsderived from vinylidene halide and mer units derived from C₄-C₅ alkylacrylate, said mer units derived from C₄-C₅ alkyl acrylate being presentin from 3 to 40 weight percent of the second copolymer, wherein saidfirst copolymer and said second copolymer are in a weight ratio of 90:10to 10:90; the first and second copolymers together form from 10 to 50weight percent of the aqueous mixture; and the aqueous mixture has a pHof 1.5 to 3.5.
 2. The composition of claim 1 wherein the first copolymercomprises from 5 to 15 weight percent of mer units derived from a C₁-C₂alkyl acrylate and the second copolymer comprises from 3 to 10 weightpercent of mer units derived from C₄-C₅ alkyl acrylate.
 3. Thecomposition of claim 1 wherein the first copolymer comprises a firstcopolymer comprising mer units of methyl acrylate and vinylidenechloride; and the second copolymer comprises mer units of butyl acrylateand vinylidene chloride.
 4. The composition of claim 1 wherein the firstand second copolymers are in a weight ratio of 90:10 to 60:40 and thefirst and second copolymers together comprise from 10 to 30 weightpercent of the aqueous mixture.
 5. The composition of claim 1 whereinthe first and second copolymers are in a weight ratio of 50:50 to 10:90and the first and second copolymers together comprise from 25 to 50weight percent of the aqueous mixture.
 6. The composition of claim 5wherein the first and second copolymers are in a weight ratio of from30:70 to 35:65.
 7. A method of inhibiting moisture vapor emission fromthe surface of a concrete structure and enhancing interfacial adhesionbetween the concrete surface and a covering thereon comprising applyingto the concrete surface an aqueous mixture of at least one firstcopolymer comprising mer units derived from vinylidene halide and merunits derived from C₁-C₂ alkyl acrylate, said mer units derived fromC₁-C₂ alkyl acrylate being present in from 5 to 40 weight percent of thefirst copolymer; and at least one second copolymer comprising mer unitsderived from vinylidene halide and mer units derived from C₄-C₅ alkylacrylate, said mer units derived from C₄-C₅ alkyl acrylate being presentin from 3 to 40 weight percent of the second copolymer, wherein saidfirst copolymer and said second copolymer are in a weight ratio of 90:10to 10:90; the first and second copolymers together form from 10 to 50weight percent of the aqueous mixture; and the aqueous mixture has a pHof 1.5 to 3.5; said aqueous mixture substantially uniformly applied tothe surface to distribute a coating having from 0.4 to 4 kg of copolymermixture per 14 m² of free surface of the concrete structure.
 8. Themethod of claim 7 wherein the first copolymer comprises from 5 to 15weight percent of mer units derived from a C₁-C₂ alkyl acrylate and thesecond copolymer comprises from 3 to 10 weight percent of mer unitsderived from C₄-C₅ alkyl acrylate.
 9. The method of claim 7 wherein thefirst copolymer comprises a copolymer of methyl acrylate and vinylidenechloride; and the second copolymer comprises a copolymer of butylacrylate and vinylidene chloride.
 10. The method of claim 7 wherein thefirst and second copolymers are in a weight ratio of 90:10 to 60:40 andthe first and second copolymers together comprise from 10 to 30 weightpercent of the aqueous mixture; said aqueous mixture is substantiallyuniformly applied to the surface to distribute from 0.4 to 2.3 kg ofcopolymer mixture per 14 m² of free surface of the concrete structure.11. The method of claim 10 wherein the aqueous mixture is applied bymultiple applications.
 12. The method of claim 7 wherein the first andsecond copolymers are in a weight ratio of 50:50 to 10:90 and the firstand second copolymers together comprise from 25 to 50 weight percent ofthe aqueous mixture; said aqueous mixture is substantially uniformlyapplied to the surface to distribute from 1.8 to 4 kg of copolymermixture per 14 m² of free surface of the concrete structure.
 13. Themethod of claim 12 wherein the first and second copolymers are in aweight ratio of from 30:70 to 35:65 and the aqueous mixture is appliedin a single application.
 14. A method of inhibiting loss of water froman uncured or partially cured concrete structure comprising applying tothe concrete surface an aqueous mixture of at least one first copolymercomprising mer units derived from vinylidene halide and mer unitsderived from C₁-C₂ alkyl acrylate, said mer units derived from C₁-C₂alkyl acrylate being present in from 5 to 40 weight percent of the firstcopolymer; and at least one second copolymer comprising mer unitsderived from vinylidene halide and mer units derived from C₄-C₅ alkylacrylate, said mer units derived from C₄-C₅ alkyl acrylate being presentin from 3 to 40 weight percent of the second copolymer, wherein saidfirst copolymer and said second copolymer are in a weight ratio of 90:10to 10:90; the first and second copolymers together form from 10 to 50weight percent of the aqueous mixture; and the aqueous mixture has a pHof 1.5 to 3.5; said aqueous mixture substantially uniformly applied tothe surface to distribute a coating having from 0.4 to 4 kg of copolymermixture per 14 m² of free surface of the concrete structure.
 15. Themethod of claim 14 wherein the first copolymer and second copolymer arein a weight ratio of 50:50 to 10:90.
 16. The method of claim 14 whereinthe first copolymer and second copolymer are in a weight ratio of 35:65to 10:90 and the first copolymer comprises mer units derived from methylacrylate and vinylidene chloride; and the second copolymer comprises merunits derived from butyl acrylate and vinylidene chloride.
 17. Thecomposition of claim 2 wherein the first copolymer comprises a firstcopolymer comprising mer units of methyl acrylate and vinylidenechloride; and the second copolymer comprises mer units of butyl acrylateand vinylidene chloride.
 18. The composition of claim 2 wherein thefirst and second copolymers are in a weight ratio of 90:10 to 60:40 andthe first and second copolymers together comprise from 10 to 30 weightpercent of the aqueous mixture
 19. The composition of claim 2 whereinthe first and second copolymers are in a weight ratio of 50:50 to 10:90and the first and second copolymers together comprise from 25 to 50weight percent of the aqueous mixture.
 20. The method of claim 8 whereinthe first copolymer comprises a copolymer of methyl acrylate andvinylidene chloride; and the second copolymer comprises a copolymer ofbutyl acrylate and vinylidene chloride.
 21. The method of claim 8wherein the first and second copolymers are in a weight ratio of 90:10to 60:40 and the first and second copolymers together comprise from 10to 30 weight percent of the aqueous mixture; said aqueous mixture issubstantially uniformly applied to the surface to distribute from 0.4 to2.3 kg of copolymer mixture per 14 m² of free surface of the concretestructure.
 22. The method of claim 8 wherein the first and secondcopolymers are in a weight ratio of 50:50 to 10:90 and the first andsecond copolymers together comprise from 25 to 50 weight percent of theaqueous mixture; said aqueous mixture is substantially uniformly appliedto the surface to distribute from 1.8 to 4 kg of copolymer mixture per14 m² of free surface of the concrete structure.